Data encoding enables digital images and videos to be compressed so that less data is needed to transmit the images or videos. To increase the amount of compression, lossy encoding can be used. Loosy encoding provides more compression at a price of some loss of image or video quality. The quality may be defined by a sum of root-mean-squared differences between relative illuminations of the original image and the image generated from encoded data, i.e., summed over the pixels entire image.
Some “lossy” encoders have control input terminals for setting either the amount of compression or the quality of the image obtainable from the encoded output data. Selecting a higher compression generally results in lower image or video quality. A reduction in image or video quality may also result from the transmission of the encoded data.